Functional morphology of the avian medullary cone

Casotti, Giovanni; Lindberg, Kimberly K.; Braun, Eldon J.

doi:10.1152/ajpregu.2000.279.5.r1722

Cited by 19 publications

(26 citation statements)

References 26 publications

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“…The loop of Henle is a structure exclusively found in birds and mammals, which are the only vertebrate groups that retain body water by producing urine osmotically more concentrated than the plasma from which it is derived (Casotti et al 2000). The kidneys of larval and adult amphibians do not develop loops of Henle.…”

Section: Discussionmentioning

confidence: 99%

The prepattern transcription factor Irx3 directs nephron segment identity

Reggiani

Raciti²,

Airik³

et al. 2007

Genes Dev.

105

169

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The nephron, the basic structural and functional unit of the vertebrate kidney, is organized into discrete segments, which are composed of distinct renal epithelial cell types. Each cell type carries out highly specific physiological functions to regulate fluid balance, osmolarity, and metabolic waste excretion. To date, the genetic basis of regionalization of the nephron has remained largely unknown.

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Section: Discussionmentioning

confidence: 99%

The prepattern transcription factor Irx3 directs nephron segment identity

Reggiani

Raciti²,

Airik³

et al. 2007

Genes Dev.

105

169

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“…Therefore, it is conceivable that Brn1 possibly suppresses apoptosis in primitive loop and Brn1 deficiency may result in premature induction of physiological apoptosis. The HL of a nephron is a unique structure that enables the generation of hypertonic urine, a function unique to birds and mammals (Casotti et al, 2000). Brn1, however, is also expressed in fish (zebrafish), suggesting that Brn1 pre-dates the establishment of HLs phylogenetically.…”

Section: Discussionmentioning

confidence: 99%

Crucial roles of Brn1 in distal tubule formation and function in mouse kidney

et al. 2003

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This study identifies a role for the gene for the POU transcription factor Brn1 in distal tubule formation and function in the mammalian kidney. Normal development of Henle's loop (HL), the distal convoluted tubule and the macula densa was severely retarded in Brn1-deficient mice. In particular, elongation and differentiation of the developing HL was affected. In the adult kidney, Brn1 was detected only in the thick ascending limb (TAL) of HL. In addition, the expression of a number of TAL-specific genes was reduced in the Brn1 +/-kidney, including Umod, Nkcc2/Slc12a1, Bsnd, Kcnj1 and Ptger3. These results suggest that Brn1 is essential for both the development and function of the nephron in the kidney.

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“…The cortical reptilian-type nephrons consist of proximal tubule, intermediate segment, distal tubule, and collecting tubule and CD [9,13]. Since they lack the loop structure (loopless nephron) and their collecting tubules open to the CD at a right angle, reptilian-type nephrons do not directly contribute to urine concentration [9,16].…”

Section: Functional Morphology Of Avian Kidney and Urine Concentrationmentioning

confidence: 99%

“…Furthermore, the hairpin turns occur in a graded fashion at various levels of the medullary cone ( Fig. 1) [13,58].…”

Section: Functional Morphology Of Avian Kidney and Urine Concentrationmentioning

confidence: 99%

Urine concentration and avian aquaporin water channels

Nishimura

2008

Pflugers Arch - Eur J Physiol

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Although birds and mammals have evolved from primitive tetrapods and advanced divergently, both can conserve water by producing hyperosmotic urine. Unique aspects in the avian system include the presence of loopless and looped nephrons, lack of the thin ascending limb of Henle's loop, a corticomedullary osmotic gradient primarily consisting of NaCl without contribution of urea, and significant postrenal modification of final urine. The countercurrent multiplier mechanism operates between the descending and ascending limbs of Henle via recycling of a single solute (NaCl) with no water accompaniment, forming an osmotic gradient along the medullary cone. Bird kidneys and developing rat kidneys share morphological and functional characteristics. Avian kidneys express aquaporin (AQP) 1, 2, and 4 homologues that share considerable homology with mammalian counterparts, but their distribution and function may not be the same. AQP2 expression in Japanese quail (q) evolves in the collecting duct of early metanephric kidneys and continues to increase in intensity and distribution during nephrogenesis and maturation. qAQP2 mRNA and protein are increased by arginine vasotocin (avian ADH), but vasotocin-induced enhancement of cAMP production and water permeability are less marked than in mammalian kidneys. Nephrogenesis is delayed by insufficient nutrition in avian embryos and newborns and results in fewer nephrons and an impaired water balance in adults. Diabetes insipidus quail with homozygous autosomal recessive mutation and an unaffected vasotocin system have low AQP2 expression, underdeveloped medullary cones. Comparative studies will provide important insight into integrative, cellular, and molecular mechanisms of epithelial water transport and its control by humoral, neural, and hemodynamic mechanisms.

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Functional morphology of the avian medullary cone

Cited by 19 publications

References 26 publications

The prepattern transcription factor Irx3 directs nephron segment identity

The prepattern transcription factor Irx3 directs nephron segment identity

Crucial roles of Brn1 in distal tubule formation and function in mouse kidney

Urine concentration and avian aquaporin water channels

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